1. Field of the Invention
The present invention relates to a method for effecting rinsing of an inverted siphon, which forms part of a sewer, and a device for performing the method.
2. Description of the Prior Art
Sewers and the like, which pass under a water course or another similar obstacle are often provided with a so called inverted siphon, i.e., a conduit which mainly in U-shape extends below the inclination line of the sewer. The inverted siphon is continuously filled with water and if the water velocity therethrough is low there is a big risk that it will be gradually silted up. Self-rinsing of inverted siphons is obtained at a certain flow velocity which is named the rinsing velocity and is dependent on the dimensions of the conduit. In the smallest inverted siphons which are generally used a water volumetric flow of about 16 l/s is required for reaching the rinsing velocity and this corresponds to the sewage volume from 300-400 small houses during the maximum period of use.
In cases where the built-up areas are smaller, which is very common, it is thus not possible to reach the criteria which are necessary for obtaining self-rinsing inverted siphons, and therefore conventional sewage pumping stations are used for giving the water a sufficient velocity through the inverted siphon to achieve rinsing. Such a pumping station is however comparatively expensive both to build and to run and it furthermore gives rise to problems for if there is any stoppage it will spill over and contaminate the receiving body of water which has often a very low discharge.